Xiao-Liang Zhang

Porphyrin and Fullerene Covalently Functionalized Graphene Hybrid Materials with Large Nonlinear Optical Properties

The nonlinear optical properties of two novel graphene nanohybrid materials covalently functionalized with porphyrin and fullerene were investigated by using the Z-scan technique at 532 nm in the nanosecond and picosecond time scale. Results show that covalently functionalizing graphene with the reverse saturable absorption chromospheres porphyrin and fullerene can enhance the nonlinear optical performance in the nanosecond regime. The covalently linked graphene nanohybrids offer performance superior to that of the individual graphene, porphyrin, and fullerene by combination of a nonlinear mechanism and the photoinduced electron or energy transfer between porphyrin or fullerene moiety and graphene.

Nonlinear optical properties of graphene oxide in nanosecond and picosecond regimes

The nonlinear optical properties of graphene oxide (GO) were investigated at 532 nm in nanosecond and picosecond regimes. Results show that two-photon absorption dominates nonlinear absorption process of GO in the case of picosecond pulses, while excited state nonlinearities play an important role in the case of nanosecond pulses. Additionally, we compared nonlinear optical properties of three different dimensional carbon-based materials (two-dimensional graphene, one-dimensional carbon nanotube, and zero-dimensional fullerene) in nanosecond and picosecond regimes, respectively. The nonlinear mechanism of GO is distinctly different from nonlinear scattering of carbon nanotube and excited state nonlinearity of fullerene.

Ultrafast carrier dynamics and saturable absorption of solution-processable few-layered graphene oxide

Ultrafast carrier dynamics and saturable absorption of few-layered graphene oxide, well-dispersed in organic solvent, are studied using femtosecond pump-probe and Z-scan techniques. The results demonstrate that few-layered graphene oxide has a fast energy relaxation of hot carriers and strong saturable absorption, which is comparable with that of reduced graphene oxide. Fast carrier relaxation combined with well solution processing capability arises from the large fraction of sp2 carbon atom inside the few-layered graphene oxide sheet together with oxidation mainly existing at the edge areas. This superiority of few-layered graphene oxide will facilitate potential applications of graphene for ultrafast photonics.

Transient thermal effect, nonlinear refraction and nonlinear absorption properties of graphene oxide sheets in dispersion.

The nonlinear refraction (NLR) properties of graphene oxide (GO) in N, N-Dimethylformamide (DMF) was studied in nanosecond, picosecond and femtosecond time regimes by Z-scan technique. Results show that the dispersion of GO in DMF exhibits negative NLR properties in nanosecond time regime, which is mainly attributed to transient thermal effect in the dispersion. The dispersion also exhibits negative NLR in picosecond and femtosecond time regimes, which are arising from sp(2)- hybridized carbon domains and sp(3)- hybridized matrix in GO sheets. To illustrate the relations between NLR and nonlinear absorption (NLA), NLA properties of the dispersion were also studied in nanosecond, picosecond and femtosecond time regimes.

Nonlinear optical and optical limiting properties of graphene oxide–Fe3O4 hybrid material

The nonlinear optical (NLO) and optical limiting properties of a graphene oxide hybrid material coordinated with Fe3O4 nanoparticles (GO–Fe3O4) were studied by using the Z-scan technique at 532 nm in the nanosecond and picosecond regimes. Results show that GO–Fe3O4 exhibits enhanced NLO and optical limiting properties in comparison with the pristine GO in the nanosecond regime. Compared with fullerene (C60) in toluene at different concentrations, GO–Fe3O4 exhibits a weaker optical limiting effect than C60 at high concentration, but shows a stronger optical limiting effect than C60 at low concentration in the high input fluence region.

Enhanced nonlinear optical properties of graphene-oligothiophene hybrid material

The nonlinear optical and optical limiting properties of an oligothiophene (6THIOP) covalently functionalized graphene hybrid material (Graphene-6THIOP) were investigated by using Z-scan technique with a 5 ns Q-switched pulsed laser at 532 nm. Results show that the hybrid material of Graphene-6THIOP exhibits enhanced nonlinear optical and optical limiting properties in comparison to individual 6THIOP, graphene moiety and C60. The enhanced nonlinear optical properties of Graphene-6THIOP should be attributed to the combination of the observed nonlinear scattering with the possible photoinduced electron or energy transfer mechanism between 6THIOP moiety and graphene.

Toward All-Carbon Electronics: Fabrication of Graphene-Based Flexible Electronic Circuits and Memory Cards Using Maskless Laser Direct Writing

Owing to its extraordinary electronic property, chemical stability, and unique two-dimensional nanostructure, graphene is being considered as an ideal material for the highly expected all-carbon-based micro/nanoscale electronics. Herein, we present a simple yet versatile approach to constructing all-carbon micro/nanoelectronics using solution-processing graphene films directly. From these graphene films, various graphene-based microcosmic patterns and structures have been fabricated using maskless computer-controlled laser cutting. Furthermore, a complete system involving a prototype of a flexible write-once-read-many-times memory card and a fast data-reading system has been demonstrated, with infinite data retention time and high reliability. These results indicate that graphene could be the ideal material for fabricating the highly demanded all-carbon and flexible devices and electronics using the simple and efficient roll-to-roll printing process when combined with maskless direct data writing.

Third-order nonlinear susceptibility tensor elements of CS2 at femtosecond time scale

The real parts of third-order nonlinear susceptibility components of CS2 are determined by polarized lights Z-Scan technique at 800 nm, and imaginary part is verified to be negligible. The contributions to susceptibility components from electron and nuclear are separated. These susceptibility values can be used as the reference values for third-order nonlinear susceptibility measurements by degenerate four-wave-mixing, optical Kerr gate/optical Kerr effect, optical heterodyne detection of optical Kerr effect, the ellipse rotation and so on.

Polarization dependence of Z-scan measurement: theory and experiment

Here we report on an extension of common Z-scan method to arbitrary polarized incidence light for measurements of anisotropic third-order nonlinear susceptibility in isotropic medium. The normalized transmittance formulas of closed-aperture Z-scan are obtained for linearly, elliptically and circularly polarized incidence beam. The theoretical analysis is examined experimentally by studying third-order nonlinear susceptibility of CS2 liquid. Results show that the elliptically polarized light Z-scan method can be used to measure simultaneously the two third-order nonlinear susceptibility components chi(3)(xyyx) and chi(3)(xxyy). Furthermore, the elliptically polarized light Z-scan measurements of large nonlinear phase shift are also analyzed theoretically and experimentally.

In situ synthesis and third-order nonlinear optical properties of CdS/PVP nanocomposite films

Cadmium sulfide (CdS) nanocrystals were in situ grown in a polyvinylpyrrolidone (PVP) matrix at room temperature using cadmium nitrate and thioacetamide as the cadmium and sulfur sources, respectively. It was found that the growth of CdS nanocrystals in the PVP matrix was well controlled and the mass concentration of CdS could be up to 18.2 wt% without the formation of large precipitates. The third-order nonlinear optical properties of the composite films were studied at 532 nm in the nanosecond regime by using the Z-scan technique. The results showed that the CdS/PVP nanocomposite film has a promising optical property exhibited by a nonlinear optical refractive index and an absorption coefficient of −1.65 × 10−11 cm2 W−1 and −4.25 × 10−7 cm W−1, respectively. The flexible processing technique allows the production of optical devices with various shapes.